A 75-year-old woman had gradually progressive binocular diplopia and 2 months later had breast cancer diagnosed. Examination showed bilateral external ophthalmoplegia with lid retraction and lag and no pupillary abnormalities. Orbital magnetic resonance imaging showed enlargement and enhancement of all extraocular muscles bilaterally. A right orbital biopsy was consistent with metastatic breast carcinoma. Positron emission tomography, bone scan, and computed tomography of the chest, abdomen, and pelvis failed to disclose other evidence of breast cancer metastases. It is unusual to encounter metastatic breast cancer affecting every extraocular muscle before the diagnosis of the primary carcinoma.